A soap supplying device is categorized into a manual soap discharge type and an automatic soap discharge type. A manual soap supplying device usually includes a soap conduit. The soap conduit communicates with a liquid soap container as well as a pressure device having a liquid soap pipe. The liquid soap pipe includes a pressure receiving section having a liquid soap chamber, a pressure applying section movable relative to the pressure receiving section and to apply pressure to the pressure receiving section, and check valves respectively disposed at two ends of the liquid soap pipe. The soap supplying device further includes a press section for a user to press thereupon to further operate the pressure receiving section. By butting the liquid soap chamber in the pressure receiving section through the pressure applying section, liquid soap in the liquid soap chamber is delivered and discharged to a hand of the user along the liquid soap pipe. An automatic soap supplying device of the prior art usually incorporates the above manual soap supplying device, which cooperates with an additional motor-driven automatic press device. As the automatic press device operates at the press section or the pressure applying section, pressure is automatically applied on the pressure receiving section by the pressure applying section to achieve liquid soap supply. Further, to adapt to a wall-mounted soap supplying device and habits of hand operations of users, a soap supplying device having a soap discharge opening facing downwards is developed.
A check valve device corresponding to a soap discharge opening is usually made of a plastic valve disposed at the soap discharge opening. By use of an elastic member, the plastic valve presses tightly against an inner wall of the soap discharge opening. When a press initiated by a user or when an automatic press device is applied, the plastic valve disengages from the inner wall to allow the liquid soap to pass through the liquid soap pipe to reach the soap discharge opening. Although the above structure is suitable for a soap supplying device that discharges the soap in an upward direction, complications are however incurred when implementing the above structure to a soap supplying device that discharges the soap in a downward direction. First of all, the liquid soap in an inverted-style liquid soap container applies a pressure to push the plastic valve due to gravitational force. In order to prevent the liquid soap from leaking through a gap between the plastic valve and the inner wall to drip onto the ground, the strength of the elastic member needs to be reinforced to render even greater tightness between the plastic valve and the inner wall. However, the increased strength of the elastic valve at the same time raises the level of force that needs to be applied for operating the pressure applying section. For example, a motor of a battery-driven automatic soap supplying device may not function properly due to insufficient power from the battery, such that the press section or the pressure applying section is not successfully propelled. Further, in a plug-in automatic soap supplying device that is free of the above issue of insufficient power from the battery, since the plastic valve is in prolonged and constant friction with the soap discharge opening, contact planes of the plastic valve and the soap discharge opening can easily become worn out. Thus, a gap between the contact planes of the plastic valve and the soap discharge opening is formed such that the liquid soap is guided through the gap to drip via the soap discharge opening.
The Taiwan Patent No. 579820 discloses a soap supplying device as described above. The soap supplying device includes a liquid soap pipe. The liquid soap pipe respectively has a liquid soap entrance and a liquid soap exit at two ends thereof. Further, the liquid soap pipe includes a roller valve at one end corresponding to the liquid soap entrance, and a plastic valve at one end corresponding to the liquid soap exit. The plastic valve is pushed by an elastic member to butt against an inner wall around the liquid soap exit on the liquid soap pipe. In this prior art, the above issue of the leaked liquid soap dripping to the ground due to inadequate tightness between the plastic valve and the inner wall of the liquid soap exit caused by the insufficiently powered motor or the wear of the plastic valve and the inner wall is likely generated.